Water-resistant portable apparatus comprising an electroacoustic transducer

ABSTRACT

The present invention concerns a water-resistant portable apparatus including a case in which there is mounted an electroacoustic transducer separated from an inlet cavity in a water-resistant manner by a deformable membrane. This inlet cavity is arranged in said case in direct communication with the exterior. The electroacoustic transducer and the inlet cavity are arranged collaterally such that at least one part of said transducer, respectively of the cavity, of a determined thickness is arranged in the same slice of the case and in that an acoustic channel connects the transducer to the membrane to transmit acoustic vibrations.

This is a National Phase Application in the United States ofInternational Patent Application No. PCT/EP2003/51047 filed Dec. 18,2003, which claims priority on European Patent Application No.03075099.6, filed Jan. 8, 2003. The entire disclosures of the abovepatent applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention concerns a water-resistant portable apparatus,such as for example a wristwatch, comprising an electroacoustictransducer.

BACKGROUND OF THE INVENTION

A water-resistant portable apparatus of this type comprises a case inwhich an electroacoustic transducer is mounted, separated in awater-resistant manner by a deformable membrane from an inlet cavity,which is arranged in the case and in direct communication with theexterior.

Such portable apparatus are known from the prior art, particularly fromEP Patent No. 0 899 635 filed in the name of the present Applicant, andincorporated herein by reference. This document discloses awater-resistant portable apparatus 1, shown in FIG. 5, comprising a case2 in which there is mounted an acoustic transducer 21 so that itcommunicates in a water-resistant manner with the exterior of case 2 viaacoustic energy. Acoustic transducer 21 is secured to a deformablemembrane 15, separating it in a water-resistant manner from an inletcavity 11 arranged in the case and in direct communication with theexterior.

A structure of this type has, however, several drawbacks. In the case ofa piezo-electric type acoustic transducer, as shown, the control circuithoused in the case on a printed circuit board or PCB comprises, inparticular, an amplifier with an integrated voltage multiplier, whichhas to be adapted to the transducer, and whose design on the PCB is morecomplex and consequently requires a larger surface.

Moreover, the connections between the piezo-electric transducer and aPCB are achieved by means of electrical wires, which requires difficultassembling operation on the transducer and operations for welding suchwires.

Furthermore, the water-resistance of the structure shown is onlyguaranteed for the elements located above the deformable membrane. Thereis no device provided for sealing any electrical or electroniccomponents located in the bottom of the case in a water-resistantmanner.

The idea consisting in simply replacing the piezo-electric type acoustictransducer with an electrodynamic type acoustic transducer, i.e. atransducer with a moving conductor in which the moving part is aconductor through which a current, provided by an external source orinduced by an external magnetic field, passes, raises difficulties asregards compactness in case, a dynamic transducer being relativelyvoluminous and whose thickness, in particular, is not negligible.

SUMMARY OF THE INVENTION

In order to overcome the drawbacks of the prior art, the idea accordingto the invention is to make a water-resistant portable apparatuscomprising a simple transducer structure occupying a reduced thicknessin the case of the apparatus.

Thus one advantageous embodiment of the invention concerns awater-resistant portable apparatus as defined in the preamble of thedescription, characterized in that the electroacoustic transducer andthe inlet cavity are arranged in a collateral manner such that at leastone part of a determined thickness of the transducer and respectivelythe cavity, are present in the same slice of the case and in that anacoustic channel connects the transducer to the membrane to transmitacoustic vibrations.

Advantageous variants are set out in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will appear during thefollowing description, given solely by way of example and made withreference to the annexed drawings, in which.

FIG. 1 shows a cross-section of the electroacoustic transducer of aportable apparatus according to a first embodiment;

FIG. 2 shows a cross-section of the electroacoustic transducer of aportable apparatus according to a second embodiment;

FIG. 3 shows a top view of the electroacoustic transducer;

FIG. 4 shows a schematic view of a dynamic loudspeaker; and

FIG. 5, already described, shows a water-resistant portable apparatus inaccordance with the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description, the various embodiments of the inventionwill be illustrated in the application thereof to a wristwatch. It isclear, however, that any other portable apparatus of small dimensions,comprising an electroacoustic transducer and capable of being immersedin a liquid such as water, to a determined depth, can form the object ofthe present invention. Furthermore, in the various embodiments shown,the electroacoustic transducer is a loudspeaker, although a transducer,such as a microphone, can also be advantageously used with thesedifferent embodiments.

Thus, according to a first embodiment of the invention, there is shownin FIG. 1, a cross-section of a wristwatch 1, guaranteed to bewater-resistant to a determined depth of water, for example a depth of30 meters, which is a value often provided in practice.

There can be seen in FIG. 1 the following parts of watch 1: the case 2,crystal 3, hands 4 and 5, dial 6, miniature motor 7, printed circuitboard or PCB 8 for the watch. All of these elements, and those shown inoutline, or not visible in this Figure, such as the quartz, the geartrain, integrated circuit, etc. are conventional and will not, thereforebe described here. It will be noted that advantageously, the watch formsa portable telephone comprising a second printed circuit board 9 for thetelephone.

In the case shown, the case comprises a back cover 10 secured in awater-resistant manner to the case by any means, for example bonding,screwing or snap fit. It will be noted that back cover 10 and case 2 canbe formed by a single moulded part. Case 2 has an inlet cavity orchamber 11 preferably of generally circular shape and in directcommunication with the exterior via an inlet channel 12, which opens outtherein laterally. Around cavity 11, case 10 has a peripheral rib 13with a rounded edge and contiguous with an annular groove 14 located onthe exterior with respect to rib 14.

A membrane 15, formed of a circular disc on which a peripheral edge 16is formed, housed in groove 14 and whose external surface is bonded to aperipheral wall 17 arranged around groove 14. Membrane 15 is compressedby an annular support surface 18 of a protective member 19, for examplea circular grid, fixedly mounted in case 2, for example by means ofscrews 20. It will be noted that membrane 15 can be held by mountingrings that are not shown, acting as a support surface, protective member19 not being necessary.

Thus, membrane 15 makes the inside of watch 1 water-resistant as regardsthe exterior. Membrane 15 is made of a water-resistant and gas-proofdeformable material, for example silicon. In a zone separate from theassembly that has just been described, back cover 10 includes a throughpassage 29 with a shoulder 30 against which there is arranged a pressurecompensation disc 31. This latter is waterproof, but pervious to air.This structure is connected to acoustic channel 24 via air passages madeinside case 2. All of these elements 29, 30 and 31 form pressurebalancing means for balancing slow variations in the differentialpressure on either side of said deformable membrane.

It will be noted, however, that deformable membrane 15 can be designedsuch that it fulfils the pressure compensation function instead of theaforementioned circuit. In such case, membrane 15 has to be made of aflexible water-resistant but gas-proof or semi-gas proof material whosestatic pressure varies at a very low frequency.

An electroacoustic transducer 21 is fixedly mounted in a housing of case2 provided for such purpose and connected by a simple electrical contact38 to printed circuit board 9. Transducer 21 and inlet cavity 11 arearranged collaterally such that at least one part of a determinedthickness of transducer 21 and respectively cavity 11 are arranged inthe same slice 28 of the case. The “slice” means the part of an objectcomprised between two parallel planes. Preferably, cavity 11 isdimensioned such that its thickness is less than or equal to that oftransducer 21, with the thickness of slice 28 of the case advantageouslycorresponding to that of transducer 21.

It will be noted that a channel 39 can also be provided inside case 2 soas to ensure that the pressure is identical above and below transducer21.

However, other arrangements wherein transducer 21 and/or cavity 11 areinclined can be envisaged, provided that one slice of the case passesthrough these two elements over a minimum determined thickness, of theorder of a millimetre, so as to reduce the total thickness of watch 1 bythe same amount.

In the case shown, electroacoustic transducer 2 is a dynamicloudspeaker, a schematic view of which and the operation of which isgiven in relation to FIG. 4. This transducer advantageously has anadditional vibrator function as is also explained in relation to FIG. 4.This dynamic transducer is controlled in a conventional manner by meansof a simple control circuit comprising in particular a standardamplifier, said control circuit being easily able to be integrated intoa reduced space of printed circuit board 9.

Transducer 21 comprises a membrane 22 of elastomeric material acting asa loudspeaker within the audible range of frequencies. The additionalvibrator function is achieved by a vibrating element that is not visiblein this Figure, for a determined frequency, allowing a good level ofvibration for watch 1, for example 140 Hertz. It will be noted that thevibrating element is preferably directed towards the inside of the caseso as to obtain better vibration for watch 1, and that flexible membrane22 is directed towards back cover 10 of the case.

In order to transmit the acoustic vibrations of membrane 22 todeformable membrane 15, there is provided in back cover 10 of the case,an acoustic channel 24, which comprises a first chamber 25 arrangedfacing membrane 22 of the transducer, a second chamber 26 arrangedfacing deformable membrane 15 and a connecting conduit 27 between thetwo chambers 25 and 26. The second chamber 26 corresponds to the zonelocated between deformable membrane 15 and protective member 19 or theback cover 10 of the case, if there is no protective member.

The behaviour of membrane 15 is as follows. When watch 1 is worn outsidewater, membrane 15 has a flat configuration in which it is free to bedeformed to transmit the acoustic vibrations produced by transducer 21to the exterior.

However, when watch 1 has just been immersed, membrane 15 will bedeformed because of an abrupt variation in the differential pressureprevailing on its two sides. It will then adopt a convex shape in thedirection of back cover 10, since the pressure compensation path throughthe circuit provided for this purpose, or through the membrane itself inthe case of a hydrophobic membrane, does not balance the pressuredifference quickly enough. From a certain hydrostatic pressure value,the deformation of membrane 15 will be such that it will be appliedagainst back cover 10 or against protective member 19, which thusprovides an efficient support preventing any deterioration of membrane15.

FIG. 2 shows a similar cross-section to that of FIG. 1, according to asecond embodiment of the invention. The reference numerals of thoseelements common to FIG. 1 have been kept the same.

As is shown, at least one electrical or electronic and preferablyvoluminous component 32, such as an accumulator, is arranged in backcover 10 of the case. It will be noted that other components can also bepresent, such as for example a printed circuit board 33 for electricallyconnecting accumulator 32 to other electrical and electronic componentsof watch 1 located in case 2.

It will be noted that, advantageously, the position of membrane 15guarantees the water-resistance of the electrical or electronic elementslocated in the top part of the case but also those located in back cover10 of the same case.

In order to be able to replace the components 32 and 33 housed in backcover 10 of the case, according to a first variant, there is provided anaccess hatch 34 closing back cover 10 in a water-resistant manner, oraccording to a second advantageous variant, a removable back cover ableto be dismantled in order to replace any components that it contains. Inthis latter case, protective member 19, already presented in FIG. 1, ispreferably provided. This latter has a dual function: it is capable onthe one hand of supporting deformable membrane 15 when external pressuregreater than a predetermined value is applied thereto and, on the otherhand, it protects membrane 15 when the back cover 10 of the case isremoved. Advantageously, this protective member 19 extends alongacoustic channel 24 so as to cover and thus also protect flexiblemembrane 22 of the dynamic loudspeaker 21.

It will be noted that the different pressure compensation alternativesare also applicable although not visible in this Figure.

FIG. 3 is a top view of certain elements of the portable apparatusaccording to the first two embodiments presented hereinbefore. Thoseelements common to the preceding Figures are designated by the samereference numerals.

FIG. 3 shows case 2, electrotransducer 21, inlet cavity 11, connectingconduit 27 of the acoustic channel between the transducer and thecavity. As is shown, cavity 11 is in direct communication with theexterior, advantageously through two inlet channels 12 a and 12 b, whichopen out therein laterally. It will be noted that these two channelshave different orientations which has the effect of improving thetransmission, respectively reception in the case of a microphone, ofacoustic vibrations towards the exterior, respectively from theexterior.

The watch includes control members, such as for example two push-buttons35 a and 36 b arranged on either side of a time setting member 36. Theoperating detail of these control members is conventional and will notbe described here. It will be noted that, preferably, channel 12 a isarranged to open out between a push-button for example button 35 a, andtime setting member 36, the other channel 12 b being off-centre so as toopen out on the other side of button 35 a.

As is visible, in the case of a telephone watch, a housing 37 is alsoprovided, located substantially in the same slice as transducer 21, forreceiving a SIM card.

It will be noted that in an application to a telephone watch, the latterpreferably includes a loudspeaker and a microphone, both being as far aspossible from each other in the case.

FIG. 4 shows a schematic cross-section of a dynamic electroacoustictransducer. First of all, a “dynamic transducer” means a transducer witha moving conductor, in which the moving part is a conductor throughwhich a current, provided by a source external to the transducer orinduced by a magnetic field external to the transducer, passes.

Such a dynamic transducer, a loudspeaker in the case shown, comprises apreferably circular case 101, connected to a magnetic circuit 102 bymeans of springs 103. An annular groove 104 made in magnetic circuit 102enables an induction coil 105 to be placed therein. A membrane 106attached to case 101 and to coil 105 allows acoustic vibrations 107 tobe transmitted in the vertical direction symbolised by an arrow. In bothembodiments presented in FIGS. 1 and 2, the transducer is advantageouslya dual function dynamic transducer, loudspeaker and vibrator. In orderto obtain the loudspeaker function by vibrating membrane 106, inparticular in audible frequency ranges (300 Hz-3.5 kHz), coil 105 iscurrent controlled by an external control circuit, not shown, thecontrol current that passes through the coil thus induces a magneticfield through the coil, which interacts with the magnetic field createdby magnetic circuit 102. In order to obtain the vibrator function, asmembrane 106 cannot vibrate sufficiently at a low frequency, the coil iscurrent controlled such that the interaction between the field inducedin the coil and the field of magnetic circuit 102 makes transducer case101 vibrate at a resonant frequency of for example 140 Hz, which thendrives the watch assembly. This type of dynamic electrotransducer isavailable particular from the Japanese Namiki Company®.

1. A water-resistant portable apparatus including a case in which thereis mounted an electroacoustic transducer separated from an inlet cavityin a water resistant manner by a deformable membrane, said inlet cavitybeing arranged in said case and in direct communication with theexterior, wherein said electroacoustic transducer and said inlet cavityare arranged collaterally such that at least one part of a determinedthickness of said transducer and respectively said cavity, are arrangedin a same slice being parallel to the bottom of said case and wherein anacoustic channel connects said transducer to said deformable membrane totransmit acoustic vibrations.
 2. The portable apparatus according toclaim 1, wherein said electroacoustic transducer is a dynamicelectroacoustic transducer.
 3. The portable apparatus according to claim1, wherein said electro acoustic transducer includes a loudspeaker. 4.The portable apparatus according to claim 3, wherein said loudspeakerincludes a flexible membrane arranged facing said acoustic channel. 5.The portable apparatus according to claim 3, wherein saidelectroacoustic transducer also includes a vibrator.
 6. The portableapparatus according to claim 5, wherein said electroacoustic transduceralso includes a vibrating element arranged toward the inside of thecase.
 7. The portable apparatus according to claim 1, wherein saidacoustic channel is arranged in the back cover of the case which isseparated from the inlet cavity in a water-resistant manner by saiddeformable membrane.
 8. The portable apparatus according to claim 7,wherein the back cover of the case forms a support surface for saiddeformable membrane when external pressure greater than a predeterminedvalue is applied thereto.
 9. The portable apparatus according to claim7, wherein at least one electrical or electronic component is arrangedin the back cover of the case.
 10. The portable apparatus according toclaim 9, wherein said electrical component is an accumulator.
 11. Theportable apparatus according to claim 7, wherein the back cover of thecase is removable, and wherein a protective member, fixedly mounted inthe case, is capable on the one hand of supporting said deformablemember when external pressure greater than a predetermined value isapplied thereto and on the other hand, of protecting said deformablemembrane when the back cover of the case is removed.
 12. The portableapparatus according to claim 11, wherein said protective member extendsalong the acoustic channel so as to also protect the flexible member ofsaid electroacoustic transducer.
 13. The portable apparatus according toclaim 1, wherein the deformable membrane is a water-resistant andgas-proof membrane and wherein the apparatus further includespressure-balancing means for balancing the slow differential pressurevariations on either side of said deformable membrane.
 14. The portableapparatus according to claim 1, wherein said portable apparatus is atelephone watch.
 15. A telephone watch according to claim 14, wherein itincludes at least one control member on the external periphery of thecase and wherein said inlet cavity is in communication with the exteriorthrough at least one inlet channel arranged in proximity to said controlmember.
 16. The telephone watch according to claim 15, wherein itincludes two inlet channels oriented along different directions.